2014 Tech study guide: FCC rules – Amateur Radio Service

The Amateur Radio Service is a service administered by the Federal Communications Commission (FCC). The FCC is the agency regulates and enforces the rules for the Amateur Radio Service in the United States. (T1A02) Part 97 is the part of the FCC regulations contains the rules governing the Amateur Radio Service. (T1A03)

Part 97.1 lists five “purposes” for the existence of amateur radio. The first is recognition of its usefulness in providing emergency and public-service communications. My favorite, enhancing international goodwill is another purpose of the Amateur Radio Service rules and regulations as defined by the FCC. (T1A05)

The rules also cite the use of amateur radio as a way to help people become better technicians and operators. Advancing skills in the technical and communication phases of the radio art is a purpose of the Amateur Radio Service as stated in the FCC rules and regulations. (T1A01) Allowing a person to conduct radio experiments and to communicate with other licensed hams around the world is a permissible use of the Amateur Radio Service. (T1A12)

Part 97 also defines terms and concepts that every amateur radio operator needs to know. For example, the FCC Part 97 definition of an amateur station is a station in the Amateur Radio Service consisting of the apparatus necessary for carrying on radio communications. (T1A10)

One of the most important concepts in amateur radio is that of harmful interference. The FCC definition of harmful interference is that which seriously degrades, obstructs, or repeatedly interrupts a radio communication service operating in accordance with the Radio Regulations. (T1A04) At no time is willful interference to other amateur radio stations permitted. (T1A11)

The Radionavigation Service is one of the services are protected from interference by amateur signals under all circumstances. (T1A06) If you are operating on the 23 cm band and learn that you are interfering with a radiolocation station outside the United States, you must stop operating or take steps to eliminate the harmful interference. (T1A14)

The FCC Part 97 definition of telemetry is a one-way transmission of measurements at a distance from the measuring instrument. (T1A07) Transmitting telemetry is one of the very few examples of a one-way amateur communication. Another is sending telecommands, usually to a satellite or radio-control model. The FCC Part 97 definition of telecommand is a one-way transmission to initiate, modify or terminate functions of a device at a distance. (T1A13)

The Frequency Coordinator is the entity that recommends transmit/receive channels and other parameters for auxiliary and repeater stations. (T1A08) Amateur operators in a local or regional area whose stations are eligible to be auxiliary or repeater stations select a Frequency Coordinator. (T1A09)

2014 Tech study guide: radio direction finding; radio control; contests; linking over the Internet; grid locators

For some odd reason, the question pool committee deleted the question about special event station callsigns and replaced it with another question about IRLP. Not only that, they added a few more questions about IRLP to this section. I think they should have kept the question about special events and eliminated the gateway question (T8C11) instead…Dan

There are many different ways to have fun with amateur radio. Contesting, for example, is a popular operating activity that involves contacting as many stations as possible during a specified period of time. (T8C03) When contacting another station in a radio contest, a good procedure is to send only the minimum information needed for proper identification and the contest exchange. (T8C04)

In VHF/UHF contests, stations often send each other their grid locators. A grid locator is a letter-number designator assigned to a geographic location. (T8C05)

One fun activity that is very practical is radio direction finding. You would use radio direction finding equipment and skills to participate in a hidden transmitter hunt, sometimes called a “fox hunt.” In addition to participating in this kind of contest, radio direction finding is one of the methods used to locate sources of noise interference or jamming. (T8C01) A directional antenna would be useful for a hidden transmitter hunt. (T8C02)

Some amateurs get licensed because they like to build and operate radio-controlled models, including boats, planes, and automobiles. The maximum power allowed when transmitting telecommand signals to radio controlled models is 1 watt. (T8C07) In place of on-air station identification when sending signals to a radio control model using amateur frequencies, a label indicating the licensee’s name, call sign and address must be affixed to the transmitter.(T8C08)

If the only radios that you have are VHF or UHF radios, you might want to look into EchoLink and the Internet Radio Linking Project (IRLP). The Internet Radio Linking Project (IRLP) is a technique to connect amateur radio systems, such as repeaters, via the Internet using Voice Over Internet Protocol. (T8C13) Voice Over Internet Protocol (VoIP),  as used in amateur radio, is a method of delivering voice communications over the Internet using digital techniques. (T8C12)

Stations that connect to EchoLink or IRLP are called nodes. One way to obtain a list of active nodes that use VoIP is from a repeater directory. (T8C09) You access an IRLP node by using DTMF signals. (T8C06) To select a specific IRLP node when using a portable transceiver, use the keypad to transmit the IRLP node ID. (T8C10)

Sometimes nodes are also called gateways. A gateway is the name given to an amateur radio station that is used to connect other amateur stations to the Internet. (T8C11)

2014 Tech study guide: satellite operation

In this section, one question was dropped and another about Keplerian elements was added…Dan

As a Technician Class licensee, you can make contacts via amateur radio satellites. Any amateur whose license privileges allow them to transmit on the satellite uplink frequency may be the control operator of a station communicating through an amateur satellite or space station. (T8B01)

Amateur satellites are basically repeaters in space. As such they have an uplink frequency, which is the frequency on which you transmit and the satellite receives, and a downlink frequency, on which the satellite transmits and you receive. As with other transmissions, the minimum amount of power needed to complete the contact should be used on the uplink frequency of an amateur satellite or space station. (T8B02)

Often, the uplink frequency and downlink frequency are in different amateur bands. For example, when a satellite is operating in “mode U/V,” the satellite uplink is in the 70 cm band and the downlink is in the 2 meter band. (T8B08)

The International Space Station often has amateur radio operators on board. Any amateur holding a Technician or higher class license may make contact with an amateur station on the International Space Station using 2 meter and 70 cm band amateur radio frequencies. (T8B04) Like most amateur satellites, the Space Station is in low earth orbit. When used to describe an amateur satellite, the initials LEO means that the satellite is in a Low Earth Orbit. (T8B10)

Amateur satellites are often equipped with beacons. A satellite beacon is a transmission from a space station that contains information about a satellite. (T8B05) FM Packet is a commonly used method of sending signals to and from a digital satellite. (T8B11)

How do you know when you are able to communicate via an amateur satellite? A satellite tracking program can be used to determine the time period during which an amateur satellite or space station can be accessed. (T8B03) The Keplerian elements are inputs to a satellite tracking program. (T8B06)

Two problems that you must deal with when communicating via satellite is Doppler shift and spin fading. Doppler shift is an observed change in signal frequency caused by relative motion between the satellite and the earth station. (T8B07) Rotation of the satellite and its antennas causes “spin fading” of satellite signals. (T8B09)

2014 Tech study guide: public service and emergency operations

There were quite a few changes to this section. Questions were added about net operations, and the question about charging a battery connecting it in parallel with a vehicle battery was moved here…Dan

One of the reasons amateur radio exists at all is that ham radio operators are uniquely set up to provide emergency and public-service communications. As a result, many hams consider it an obligation to be prepared to help out when called upon to do so. This includes having the proper equipment and knowing the proper operating procedures.

There are two organizations that provide emergency communications: the Radio Amateur Civil Emergency Service (RACES) and the Amateur Radio Emergency Service (ARES). The thing that both RACES and ARES have in common is that both organizations may provide communications during emergencies. (T2C04) The Amateur Radio Emergency Service (ARES) is a group of licensed amateurs who have voluntarily registered their qualifications and equipment for communications duty in the public service. (T2C12) All of these choices are correct when describing the Radio Amateur Civil Emergency Service (RACES) (T2C05):

  • A radio service using amateur frequencies for emergency management or civil defense communications
  • A radio service using amateur stations for emergency management or civil defense communications
  • An emergency service using amateur operators certified by a civil defense organization as being enrolled in that organization

When an emergency occurs, it’s common for amateur radio operators to form a network or “net” to facilitate emergency communications. The net is led by the net control station, whose job it is to make sure that messages are passed in an efficient and timely manner.

Stations other than the net control station are said to “check into” the net. An accepted practice for an amateur operator who has checked into an emergency traffic net is to remain on frequency without transmitting until asked to do so by the net control station. (T2C07) There are, however, times when a station may need to get the immediate attention of the net control station. If this is the case, an accepted practice to get the immediate attention of a net control station when reporting an emergency is to begin your transmission by saying “Priority” or “Emergency” followed by your call sign. (T2C06)

The term for messages passed between stations in an emergency net is “traffic,” and the process of passing messages to and from amateur radio stations is called “handling traffic.” Message traffic may be formal or informal. A characteristic of good emergency traffic handling is passing messages exactly as received. (T2C08) To insure that voice message traffic containing proper names and unusual words are copied correctly by the receiving station, such words and terms should be spelled out using a standard phonetic alphabet. (T2C03)

Formal traffic messages consists of four parts: preamble, address, text, signature. The preamble in a formal traffic message is the information needed to track the message as it passes through the amateur radio traffic handling system. (T2C10) Part of the preamble is the check. The check is a count of the number of words or word equivalents in the text portion of the message. (T2C11) The address is the name and address of the intended recipient, the text is the message itself, and the signature is the part of the message that identifies the originator of the message.

An important thing to remember is that FCC rules always apply to the operation of an amateur station. (T2C01) Amateur station control operators are permitted to operate outside the frequency privileges of their license class only if necessary in situations involving the immediate safety of human life or protection of property. (T2C09)

In an emergency situation, amateur radio operators often find themselves using battery power. It is, therefore, important to keep batteries charged and ready to go. One way to recharge a 12-volt lead-acid station battery if the commercial power is out is to connect the battery in parallel with a vehicle’s battery and run the engine. (T2C02)

2014 Tech study guide: operating procedures

I’m going to lump several sections into this one post. Several questions were added and several updated, but nothing really major was changed….Dan

FM Operation 

Once they get their licenses, most Technicians purchase a VHF/UHF FM transceiver. This type of radio allows them to use repeaters and participate in public-service events.

To use repeaters, you need to know how to set up your radio. Repeaters receive on one frequency and transmit on another. You program your radio so that it receives on the repeater’s transmit frequency and transmits on the repeater’s receive frequency.

The difference between the transmit frequency and receive frequency is called the repeater frequency offset. Plus or minus 600 kHz is the most common repeater frequency offset in the 2 meter band. (T2A01) Plus or minus 5 MHz is a common repeater frequency offset in the 70 cm band. (T2A03)

Repeater operation is called duplex operation because you’re transmitting and receiving on two different frequencies. When the stations can communicate directly without using a repeater, you should consider communicating via simplex rather than a repeater. (T2B12) Simplex communication is the term used to describe an amateur station that is transmitting and receiving on the same frequency. (T2B01)

To help amateurs operating simplex finding one another, frequencies on each band have been set aside as “national calling frequencies.” 446.000 MHz is the national calling frequency for FM simplex operations in the 70 cm band. (T2A02) 146.52 MHz is the national calling frequency for FM simplex operation in the 2 m band.

Because repeaters often operate in environments where there is a lot of interference they are programmed not to operate unless the station they are receiving is also transmitting a sub- audible tone of a specific frequency. These tones are sometimes called PL (short for “private line”) tones or CTCSS tones. CTCSS is the term used to describe the use of a sub-audible tone transmitted with normal voice audio to open the squelch of a receiver. (T2B02) If your radio has not been programmed to transmit the proper sub-audible tone when you transmit, the repeater will not repeat your transmission.

All of these choices are correct when talking about common problems that might cause you to be able to hear but not access a repeater even when transmitting with the proper offset: (T2B04)

• The repeater receiver requires audio tone burst for access
• The repeater receiver requires a CTCSS tone for  access
• The repeater receiver may require a DCS tone sequence for access

One of the controls on a VHF/UHF transceiver is the squelch control. Carrier squelch is the term that describes the muting of receiver audio controlled solely by the presence or absence of an RF signal. (T2B03) You can set this control so that you only get an audio output when receiving a signal.

Microphone gain is also an important control. The reason for this is that the amplitude of the modulating signal determines the amount of deviation of an FM signal. (T2B05) When the deviation of an FM transmitter is increased, its signal occupies more bandwidth. (T2B06) One thing that could cause your FM signal to interfere with stations on nearby frequencies is that you have set your microphone gain too high, causing over-deviation. (T2B07)

In addition to knowing how to set the controls of your radio, you need to know the protocol for making contacts. First, when using a repeater, it is rare to hear stations calling CQ. In place of “CQ,” say your call sign to indicate that you are listening on a repeater. (T2A09) An appropriate way to call another station on a repeater if you know the other station’s call sign is to say the station’s call sign then identify with your call sign. (T2A04)

HF Operation

On the HF bands, when you want to contact another station, you “call CQ.” That is to say, you would say something like, “CQ CQ CQ. This is KB6NU.” The meaning of the procedural signal “CQ” is calling any station. (T2A08) All of these choices are correct when choosing an operating frequency for calling CQ (T2A12):

  • Listen first to be sure that no one else is using the frequency
  • Ask if the frequency is in use
  • Make sure you are in your assigned band

When responding to a call of CQ, you should transmit the other station’s call sign followed by your call sign. (T2A05) For example, if W8JNZ heard my call and wanted to talk to me, he would reply, “KB6NU this is W8JNZ. Over.” Then, I would return the call, and our contact would begin.

It’s important to always identify your station, even when only performing tests. An amateur operator must properly identify the transmitting station when making on-air transmissions to test equipment or antennas. (T2A06) When making a test transmission, station identification is required at least every ten minutes during the test and at the end. (T2A07)

As a technician, you will be able to operate Morse Code on certain portions of the 80 m, 40 m, 15 m, and 10 m bands. To shorten the number of characters sent during a CW contact, amateurs often use three-letter combinations called Q-signals. QRM is the “Q” signal used to indicate that you are receiving interference from other stations. (T2B10) The “Q” signal used to indicate that you are changing frequency is QSY. (T2B11)

General Guidelines

FCC rules specify broadly where amateur radio operators have operating privileges, but are not very detailed. Band plans take this one step further, suggesting where amateurs should use certain modes. While consulting a band plan before operating is a good idea, realize that a band plan is a voluntary guideline for using different modes or activities within an amateur band. (T2A10)

Regarding power levels used in the amateur bands under normal, non-distress circumstances, the FCC rules state that, while not exceeding the maximum power permitted on a given band, use the minimum power necessary to carry out the desired communication. (T2A11) So, while you are authorized to use up to 1,500 W output power on VHF and above (200W on HF), you really should only use that much power when you really need it.

The basics of good operation include keeping your signals clean and avoid interference to other stations. When two stations transmitting on the same frequency interfere with each other, common courtesy should prevail, but no one has absolute right to an amateur frequency. (T2B08)

When identifying your station when using phone, use of a phonetic alphabet is encouraged by the FCC. (T2B09) Most hams around the world understand and use the NATO, or ITU phonetic alphabet. Learn it and use it.

2014 Tech study guide: Basic repair and testing

The addition of T7D12 is the only change to this section…Dan

The most common test instrument in an amateur radio shack is the multimeter. Multimeters combine into a single instrument the functions of a voltmeter, ohmmeter, and ammeter. Voltage and resistance are two measurements commonly made using a multimeter. (T7D07)

You use a voltmeter to measure electric potential or electromotive force. (T7D01) The correct way to connect a voltmeter to a circuit is in parallel with the circuit. (T7D02) When measuring high voltages with a voltmeter, one precaution you should take is to ensure that the voltmeter and leads are rated for use at the voltages to be measured. (T7D12)

An ohmmeter is the instrument used to measure resistance. (T7D05) When measuring circuit resistance with an ohmmeter ensure that the circuit is not powered. (T7D11) Attempting to measure voltage when using the resistance setting might damage a multimeter. (T7D06) What is probably happening when an ohmmeter, connected across a circuit, initially indicates a low resistance and then shows increasing resistance with time is that the circuit contains a large capacitor. (T7D10)

An ammeter is the instrument used to measure electric current. (T7D04) An ammeter is usually connected to a circuit in series with the circuit. (T7D03)

In addition to knowing how to make electrical measurements, knowing how to solder is an essential skill for amateur radio operators. Rosin-core solder is best for radio and electronic use. (T7D08) A grainy or dull surface is the characteristic appearance of a “cold” solder joint. (T7D09)

2014 Tech study guide: RF interference, common transmitter and receiver problems

There were some substantial changes to this section. More questions were added about how to troubleshoot RF interference problems and a couple of questions were eliminated, including one about alternator whine…Dan

Since Murphy’s Law—the law that states if anything can go wrong, it will—applies to amateur radio as much as it does to any other pursuit, at some point you will have to deal with problems. These may include overload, distortion, feedback, and interference.

Let’s first consider interference. All of these choices are correct when talking about causes of radio frequency interference (T7B03):

  • fundamental overload
  • harmonics
  • spurious emissions.

Any of these could cause interference to a TV set or radio, and you will want to take steps to find and eliminate that interference. If someone tells you that your station’s transmissions are interfering with their radio or TV reception, you should first make sure that your station is functioning properly and that it does not cause interference to your own radio or television when it is tuned to the same channel or frequency. (T7B06)

While it’s not very likely that your amateur radio station will interfere with a neighbor’s cable TV service, it can sometimes occur. The first step to resolve cable TV interference from your ham radio transmission is to be sure all TV coaxial connectors are installed properly. (T7B12)

Your amateur radio station may interfere with a nearby radio receiver if your signal is so strong that the receiver cannot reject the signal even though your signal is not on the frequency to which the receiver is tuned. When a receiver is unable to reject strong signals outside the AM or FM band, it can cause a broadcast AM or FM radio to receive an amateur radio transmission unintentionally. (T7B02) One way to reduce or eliminate the overloading of a non-amateur radio or TV receiver by an amateur signal is to block the amateur signal with a filter at the antenna input of the affected receiver. (T7B05)

Another device that often experiences interference from amateur radio stations is the telephone. The telephone wires act as antenna and the telephone itself demodulates the signal. One way to reduce or eliminate interference by an amateur transmitter to a nearby telephone is to install an RF filter at the telephone. (T7B04)

All of these choices are correct when considering what may be useful in correcting a radio frequency interference problem (T7B07):

  • Snap-on ferrite chokes
  • Low-pass and high-pass filters
  • Band-reject and band-pass filters

Interference works both ways. Your neighbors may have wireless devices, sometimes called “Part 15 devices,” that can interfere with your station. A Part 15 device is an unlicensed device that may emit low powered radio signals on frequencies used by a licensed service. (T7B09) All of these choices are correct when considering what you should do if something in a neighbor’s home is causing harmful interference to your amateur station (T7B08):

  • Work with your neighbor to identify the offending device
  • Politely inform your neighbor about the rules that require him to stop using the device if
    it causes interference
  • Check your station and make sure it meets the standards of good amateur practice

Perhaps the most common problem that amateur radio operators have is distorted or noisy audio when transmitting. There are many reasons for poor audio. All of these choices are correct if you receive a report that your audio signal through the repeater is distorted or unintelligible (T7B10):

  • Your transmitter may be slightly off frequency
  • Your batteries may be running low
  • You could be in a bad location

Reports of garbled, distorted, or unintelligible transmissions is a symptom of RF feedback in a transmitter or transceiver. (T7B11) Sometimes, garbled or distorted audio when operating FM is the result of over-deviation. Talk farther away from the microphone is one thing you can do if you are told your FM handheld or mobile transceiver is over-deviating. (T7B01)

2014 Tech study guide: receivers, transmitters, and transceivers

This section was changed quite a bit. It used to include four block diagrams, but the question pool committee eliminated all of them. Bravo! Dan

In the early days of radio, amateur radio operators used separate receivers and transmitter units. Nowadays, however, most use radios called transceivers. A  transceiver is a unit combining the functions of a transmitter and a receiver. (T7A02)

There are many different types of transceivers. A multi-mode VHF transceiver is the type of device that is most useful for VHF weak-signal communication. (T7A09) Instead of purchasing a multi-mode VHF transceiver, many amateurs use a transverter to convert the signals from their HF transceiver to the VHF, UHF, and even microwave bands. For example, a device that would take the output of a low-powered 28 MHz SSB exciter and produces a 222 MHz output signal is a transverter. (T7A06)

Many, if not most, new amateurs purchase a handheld transceiver, sometimes called a “handie-talkie,” or HT, as their first transceiver. One disadvantage of of using a handheld transceiver is that the maximum output power is generally only 5 W, and because of this, they have limited range. To increase the low-power output of a handheld transceiver, and therefore its, range, you can use an RF power amplifier. (T7A10)

When talking about a transceivers specifications, we still refer to its receiver and transmitter. The two most important specifications for a receiver are sensitivity and selectivity. Sensitivity is the term that describes the ability of a receiver to detect the presence of a signal. (T7A01) The term that describes the ability of a receiver to discriminate between multiple signals is selectivity. (T7A04)

To improve the sensitivity of a receiver, you can use an RF preamplifier. An RF preamplifier is installed between the antenna and receiver. (T7A11)

Most HF transceivers have some version of a superheterodyne receiver. In a superheterodyne receiver, we first convert an incoming radio signal from its frequency to an intermediate frequency, or IF. The circuit that does this is the mixer. A mixer is used to convert a radio signal from one frequency to another. (T7A03)

When transmitting, we want to generate an RF signal with a specific frequency. To do that, we use an oscillator. Oscillator is the name of a circuit that generates a signal of a desired frequency. (T7A05)

To transmit a voice signal we have to combine an audio frequency signal from the microphone with the RF carrier signal generated by the transmitter. Modulation is the term that describes combining speech with an RF carrier signal. (T7A08) Modulators use a type of mixer circuit to accomplish this process.

2014 Tech study guide: operating controls

Question T4B12 about the function of automatic gain control was added to this section…Dan

To properly operate a transceiver, you need to know how to use the controls. Perhaps the most important transmitter control is microphone gain. If a transmitter is operated with the microphone gain set too high, the output signal might become distorted. (T4B01)

You also need to know how to set the operating frequency of your transceiver. The keypad or VFO knob can be used to enter the operating frequency on a modern transceiver. (T4B02) A way to enable quick access to a favorite frequency on your transceiver is to store the frequency in a memory channel. (T4B04)

A common receiver control on VHF/UHF transceivers is the squelch control. The purpose of the squelch control on a transceiver is to mute receiver output noise when no signal is being received. (T4B03) If set too high, then you will not be able to hear low-level signals.

Another common setting on VHF/UHF transceivers is the offset frequency. This is especially important when operating repeaters. The common meaning of the term “repeater offset” is the difference between the repeater’s transmit and receive frequencies. (T4B11)

A common receiver control on HF transceivers is the RIT control. The term “RIT” means Receiver Incremental Tuning. (T4B07) The receiver RIT or clarifier are controls that could be used if the voice pitch of a single-sideband signal seems too high or low. (T4B06)

Another common control on a receiver is the automatic gain control, or AGC. Its function is to keep received audio relatively constant. (T4B12) This is important because HF signal strengths can vary widely. and that can cause audio levels to vary widely as well.

HF transceivers are often equipped with a variety of different filters. The advantage of having multiple receive bandwidth choices on a multimode transceiver is that it permits noise or interference reduction by selecting a bandwidth matching the mode. (T4B08) For example, 2400 Hz is an appropriate receive filter to select in order to minimize noise and interference for SSB reception. (T4B09) 500 Hz is an appropriate receive filter to select in order to minimize noise and interference for CW reception. (T4B10)

2014 Tech study guide: station setup

There were two question changes in this section. Question T4A02 was changed from a question about headphones to a question about using computers in the shack. Question T4A05 was changed from a question about band-reject filters to one about using an SWR meter. I’ve added that question to the appropriate section…Dan

When setting up an amateur radio station, choosing the radio itself is the most important consideration, but you must also choose a wide range of accessories, such as power supplies and microphones. In addition, how you set up the station is important for it to operate efficiently.

One accessory that you’ll definitely need is a power supply to provide the DC voltage and current that your radio needs. A good reason to use a regulated power supply for communications equipment is that it prevents voltage fluctuations from reaching sensitive circuits. (T4A03) When choosing a supply, check the voltage and current ratings of the supply and be sure to choose one capable of supplying a high enough voltage and enough current to power your radio.

If you are going to operate with one of the voice modes, you’ll need a microphone. When considering the microphone connectors on amateur transceivers, note that some connectors include push-to-talk and voltages for powering the microphone. (T4A01)

A computer has become a very common accessory in an amateur radio “shack.” All of these choices are correct when talking about how a computer be used as part of an amateur radio station (T4A02):

  • For logging contacts and contact information
  • For sending and/or receiving CW
  • generating and decoding digital signals

If you plan to operate packet radio, you will need a computer and a terminal controller, or TNC, in addition to the radio. A terminal node controller would be connected between a transceiver and computer in a packet radio station. (T4A06) The TNC converts the ones and zeroes sent by the computer into tones sent over the air.

A more modern way to operate digital modes, such as RTTY or PSK-31, is to use a computer equipped with a sound card. When conducting digital communications using a computer, the sound card provides audio to the microphone input and converts received audio to digital form. (T4A07) The sound card may be connected directly to the radio, but it’s usually better to connect it through a device that isolates the radio from the computer. This prevents ground loops from causing the signal to be noisy.

Audio and power supply cables in a amateur radio station sometimes pick up stray RF. At minimum, this RF can cause the audio to be noisy. At worst, it can cause a radio or accessory to malfunction. To reduce RF current flowing on the shield of an audio cable (or in a power supply cable), you would use a ferrite choke. (T4A09)

Modern radio equipment is very well-designed, and harmonic radiation is rarely a problem these days. Even so, there may be times when it does become a problem, and you’ll have to take steps to attenuate the harmonics. To reduce harmonic emissions, a filter must be installed between the transmitter and the antenna. (T4A04)

Good grounding techniques can help you avoid interference problems. When grounding your equipment, you should connect the various pieces of equipment to a single point, keep leads short, and use a heavy conductor to connect to ground. Flat strap is the type of conductor that is best to use for RF grounding. (T4A08)

If you plan to install a radio in your car and operate mobile, you have a different set of challenges. One is connecting the radio to the car’s power system. Some amateurs connect their radio with a cigarette lighter plug, but this plug is not designed for high currents. Instead, a mobile transceiver’s power negative connection should be made at the battery or engine block ground strap. (T4A11) The positive connection can also be made at the battery or through an unused position of the vehicle’s fuse block.

Another challenge is noise generated by the car itself. One thing that could be happening if another operator reports a variable high-pitched whine on the audio from your mobile transmitter is that noise on the vehicle’s electrical system is being transmitted along with your speech audio. (T4A12)

The alternator is often the culprit.  The alternator is the source of a high-pitched whine that varies with engine speed in a mobile transceiver’s receive audio. (T4A10) Should this be a problem, there are filters that you can install to mitigate the alternator whine. One thing that would reduce ignition interference to a receiver is to turn on the noise blanker. (T4B05)